Techniques for positioning therapy delivery elements within a spinal cord or a brain

ABSTRACT

The present invention addresses the problems associated with lead migration, patient movement or position, histological changes, neural plasticity or disease progression. The present invention discloses techniques for implanting a lead having therapy delivery elements, such as electrodes or drug delivery ports, within a vertebral or cranial bone so as to maintain these elements in a fixed position relative to a desired treatment site. The therapy delivery elements may thereafter be adjusted in situ with a position control mechanism and/or a position controller to improve the desired treatment therapy. The present invention also discloses techniques for non-invasively positioning and re-positioning therapy delivery elements after implant to provide electrical stimulation and/or drug infusion to a precise target. A position control mechanism and/or a position controller are provided for adjusting in situ the position of the therapy delivery elements relative to the targeted tissue of interest. The therapy delivery elements may be positioned laterally in any direction relative to the targeted treatment site or toward or away from the targeted treatment site. A control system may be provided for open- or closed-loop feedback control of the position of the therapy delivery elements as well as other aspects of the treatment therapy.

[0001] This patent application is a continuation-in-part of the earlierfiled copending patent application Ser. No. 09/070,136 entitled“Apparatus and Method for Expanding a Stimulation Lead Body in Situ,”filed on Apr. 30, 1996, for which priority is claimed. This parentapplication is incorporated herewith by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to stimulation or drug deliverysystems, and more particularly relates to techniques for positioning thetreatment therapy elements, such as electrodes or catheters, to providemore effective treatment therapy.

[0004] 2. Description of Related Art

[0005] Electrical stimulation techniques have become increasinglypopular for treatment of pain and various neurological disorders.Typically, an electrical lead having one or more electrodes is implantednear a specific site in the brain or spinal cord of a patient. The leadis coupled to a signal generator which delivers electrical energythrough the electrodes to nearby neurons and neural tissue. Theelectrical energy delivered through the electrodes creates an electricalfield causing excitation of the nearby neurons to directly or indirectlytreat the pain or neurological disorder.

[0006] Presently, only highly skilled and experienced practitioners areable to position a stimulation lead in such a way that the desiredoverlap between stimulation sites and target tissue is reached anddesired results are obtained over time with minimal side effects. Itrequires much time and effort to focus the stimulation on the desiredbody region during surgery. These leads cannot be moved by the physicianwithout requiring a second surgery.

[0007] The major practical problem with these systems is that even ifthe paresthesia (sensation of stimulation) location covers the pain areaperfectly during surgery, the required paresthesia pattern often changeslater due to lead migration, histological changes (such as the growth ofconnective tissue around the stimulation electrode), neural plasticityor disease progression. As a result, the electrical energy may stimulateundesired portions of the brain or spinal cord.

[0008] Maintaining the lead in a fixed position and in proximity to thetreatment site is therefore highly desirable. Presently known systemsare susceptible to lead migration. Accordingly, the lead may migratesuch that the targeted tissue is outside of the effective steerabletreatment range of the lead. Additionally, for some treatmentapplications, the lead just cannot be placed optimally to provide thedesired treatment therapy. For example, in the case of treatment oflower back pain, electrical stimulation may be provided at the middlethoracic vertebral segments, T6-T9. With currently available systems,this often fails mostly due to the great thickness of the cerebralspinal fluid (CSF) layer.

[0009] Alternatively, it is desirable to redirect paresthesia withoutrequiring a second surgery to account for lead migration, histologicalchanges, neural plasticity or disease progression. With present singlechannel approaches, however, it is difficult to redirect paresthesiaafterwards, even though limited readjustments can be made by selecting adifferent contact combination, pulse rate, pulse width or voltage. Theseproblems are found not only with spinal cord stimulation (S CS), butalso with peripheral nerve stimulation (PNS), depth brain stimulation(DBS), cortical stimulation and also muscle or cardiac stimulation.Similar problems and limitations are present in drug infusion systems.

[0010] Recent advances in this technology have allowed the treatingphysician or the patient to steer the electrical energy delivered by theelectrodes once they have been implanted within the patient. Forexample, U.S. Pat. No. 5,713,922 entitled “Techniques for Adjusting theLocus of Excitation of Neural Tissue in the Spinal Cord or Brain,”issued on Feb. 3, 1998 to and assigned to Medtronic, Inc. discloses onesuch example of a steerable electrical energy. Other techniques aredisclosed in application Ser. No. 08/814,432 (filed Mar. 10, 1997) andSer. No. 09/024,162 (filed Feb. 17, 1998). Changing the electric fielddistribution changes the distribution of neurons recruited during astimulus output, and thus provides the treating physician or the patientthe opportunity to alter the physiological response to the stimulation.The steerability of the electric field allows the user to selectivelyactivate different groups of nerve cells without physically moving thelead or electrodes.

[0011] These systems, however, are limiting in that the steerableelectric field is limited by the location of the electrodes. If theelectrodes move outside of the desired treatment area or if the desiredstimulation area is different due to histological changes or diseasemigration, the desired treatment area may not be reached even by thesesteerable electrodes. Further, even if these steerable electrodes may beable to stimulate the desired neural tissue, the distance from theelectrodes to the tissue may be too large such that it would requiregreater electrical power to provide the desired therapy. It has beenshown that only a fraction of the current from modem stimulation devicesgets to the neurons of interest. See W. A. Wesselink et al. “Analysis ofCurrent Density and Related Parameters in Spinal Cord Stimulation,” IEEETransactions on Rehabilitation Engineering, Vol. 6, pp. 200-207 (1998).This not only more rapidly depletes the energy reserve, but it also maystimulate undesired neural tissue areas thereby creating undesired sideeffects such as pain, motor affects or discomfort to the patient.

[0012] In short, there remains a need in the art to provide anelectrical stimulation device that is not susceptible to lead migrationand that may be positioned in proximity to the treatment site. Inaddition, there remains a need in the art to provide an electricalstimulation device that may be adjusted to account for lead migration,patient movement or position, histological changes, and diseasemigration.

SUMMARY OF THE INVENTION

[0013] As explained in more detail below, the present inventionovercomes the above-noted and other shortcomings of known electricalstimulation and drug delivery techniques. The present invention providesa technique for positioning therapy delivery elements, such aselectrodes and/or catheters, optimally closer to the desired treatmentarea. The present invention includes a therapy delivery device such as asignal generator or a drug pump, at least one lead having at least onetherapy delivery element coupled to the therapy delivery device and atleast one position control mechanism coupled to the therapy deliveryelements for adjusting the position of the therapy delivery elementrelative to the excitable tissue of interest. The position may beadjusted laterally in any number of directions relative to the lead ortoward or away from the excitable tissue of interest. Any number ofposition control mechanisms may be incorporated to selectively adjustthe position of the therapy delivery elements. Also, a positioncontroller such as a microprocessor may be utilized to operate theposition control mechanism to position the therapy delivery elements.

[0014] In other embodiments of the present invention, one or more oftherapy delivery elements may be placed within the cranial or vertebralbone of the patient so as to maintain the therapy delivery elements in afixed position relative to the targeted neural tissue. The therapydelivery elements may thereafter be adjusted with a position controlmechanism and/or a position controller to improve the desired treatmenttherapy.

[0015] By using the foregoing techniques, therapy delivery elements maybe positioned to provide treatment therapy such as electricalstimulation and/or drug infusion to a precise target. Additionally, thepresent invention accounts for the problems associated with leadmigration, histological changes, neural plasticity or diseaseprogression.

[0016] Optionally, the present invention may incorporate a closed-loopsystem which may automatically adjust (1) the positioning of the therapydelivery elements in response to a sensed condition of the body such asa response to the treatment therapy; and/or (2) the treatment therapyparameters in response to a sensed symptom or an important relatedsymptom indicative of the extent of the disorder being treated.

[0017] Examples of the more important features of this invention havebeen broadly outlined above so that the detailed description thatfollows may be better understood and so that contributions which thisinvention provides to the art may be better appreciated. There are, ofcourse, additional features of the invention which will be describedherein and which will be included within the subject matter of theclaims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and other advantages and features of the invention willbecome apparent upon reading the following detailed description andreferring to the accompanying drawings in which like numbers refer tolike parts throughout and in which:

[0019]FIG. 1 depicts a neurostimulation device in accordance with anembodiment of the present invention;

[0020]FIG. 2 is a cross-sectional view of spinal cord at spinal bonelevel T-6 having an implanted lead in accordance with a preferredembodiment of the present invention;

[0021]FIG. 3 illustrates a position controller having metal bellows;

[0022]FIG. 4 illustrates a position controller having a piston;

[0023] FIGS. 5A-D disclose embodiments of the present invention whereelectrodes are anchored within vertebral bones of the spinal cord;

[0024]FIG. 6 discloses another embodiment of the present inventionhaving a collar screwed into vertebral bone;

[0025]FIG. 7 discloses another embodiment of the present inventionhaving a collar with an “O” ring to hold an electrode housing inposition by pressure;

[0026]FIGS. 8 and 9 disclose other embodiments of the present inventionwhere a plurality of electrodes are anchored through vertebral bones ofthe spinal cord;

[0027]FIG. 10 discloses another embodiment of the present inventionwhere a balloon is implemented on a dorsal side of a paddle lead;

[0028]FIG. 11 illustrates an alternative technique for adding orremoving fluid to a balloon;

[0029] FIGS. 12A-B depict other embodiments wherein a plurality ofballoons are implemented to allow more selective adjustment of theelectrodes relative to the spinal cord;

[0030] FIGS. 13A-B illustrate another embodiment wherein the balloonincludes a rigid or semirigid dorsal component;

[0031] FIGS. 14A-B illustrate yet another embodiment wherein the balloonincludes a rigid or semi-rigid dorsal component having a hinge;

[0032]FIG. 15 depicts another embodiment of a reservoir system foradjusting fluid amounts in a lead;

[0033]FIG. 16 depicts yet another embodiment a reservoir system foradjusting fluid amounts in a lead;

[0034] FIGS. 17A-D disclose other embodiments whereby a portion of thelead body thickness is adjusted using gliders;

[0035] FIGS. 18A-C disclose yet other embodiments whereby a portion ofthe lead body thickness is adjusted using movable wires;

[0036]FIG. 19 discloses yet another embodiments whereby a portion of thelead body thickness is adjusted using a piston and a spring;

[0037]FIG. 20 discloses yet another embodiment whereby a portion of thelead body thickness is adjusted using a gear mechanism;

[0038] FIGS. 21A-C disclose various embodiments of the present inventionutilizing a single or dual gear mechanism;

[0039]FIGS. 22 and 23 illustrate embodiments of the present inventionwhere more than one of the elements of the above figures above areimplemented;

[0040]FIG. 24 illustrates yet another embodiment of a lead having twospans extending laterally from its body;

[0041]FIG. 25 illustrates yet another embodiment of a lead having twospans that are adjustable by use of guide struts;

[0042]FIG. 26 discloses an embodiment of a paddle lead having movablelateral spans;

[0043] FIGS. 27A-B disclose yet another embodiment of a paddle leadcapable of extending electrodes laterally;

[0044]FIG. 28 is a schematic block diagram of a sensor and an analog todigital converter circuit used in a preferred embodiment of theinvention;

[0045]FIG. 29 is a flow chart illustrating a preferred form of amicroprocessor program for utilizing the sensor to control the treatmenttherapy provided to the neural tissue;

[0046]FIG. 30 is a schematic block diagram of a microprocessor andrelated circuitry used in a preferred embodiment of the invention;

[0047] FIGS. 31-35 are flow charts illustrating a preferred form of amicroprocessor program for generating stimulation pulses to beadministered to neural tissue;

[0048] FIGS. 36A-D illustrate other embodiments of a lead beingimplanted within a vertebral bone of a patient;

[0049] FIGS. 37A-B illustrate an embodiment of an extendable lead forimplant within a brain; and

[0050] FIGS. 38A-C illustrate an embodiment of the present inventionwherein a plurality of MCE's are implanted within the skull of apatient.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051]FIG. 1 depicts a neurostimulation therapy delivery device 14 inaccordance with an embodiment of the present invention. Therapy deliverydevice 14 made in accordance with the preferred embodiment is preferablyimplanted below the skin of a patient or, alternatively, may be anexternal device. Therapy delivery device 14 may be implanted as shown inFIG. 1, in the abdomen or any other portion of the body 10. One or moreleads 23 are positioned to stimulate a specific site in a spinal cord12. Therapy delivery device 14 may take the form of a modified signalgenerator Model 7424 manufactured by Medtronic, Inc. under the trademarkItrel II which is incorporated by reference in its entirety. Lead 23 maytake the form of any of the leads sold with the Model 7424, forstimulating a spinal cord, and is coupled to therapy delivery device 14by one or more conventional conductors 16 and 18. Lead 23 may include apaddle lead, a lead having one or more therapy delivery devices such asstimulation electrodes and/or catheters, or a combination catheter/leadcapable of providing electrical stimulation and drug delivery. Lead 23may also have recording electrodes. Exemplary embodiments of lead 23incorporating the principles of the present invention are shown in thefigures of the present application and discussed herein.

[0052] As shown in FIG. 1, the distal end of lead 23 terminates in oneor more therapy delivery elements such as stimulation electrodesgenerally implanted into or near a selected portion of the spinal cordby conventional surgical techniques. The location of the electrodes isdetermined by the type of treatment that is desired. Any number ofelectrodes may be used for various applications. Each of the electrodesare preferably individually connected to therapy delivery device 14through lead 23 and conductors 16 and 18. Lead 23 is surgicallyimplanted either by a laminotomy or by a percuntaneous needle.

[0053] Therapy delivery device or signal generator 14 may programmed toprovide a predetermined stimulation dosage in terms of pulse amplitude,pulse width, pulse frequency, or duty cycle. As preferred, a programmer20 may be utilized to provide stimulation parameters to therapy deliverydevice 14 via telemetry. Programmer is coupled to an antenna 24 viaconductor 22.

[0054] The system may optionally include one or more sensors to provideclosed-loop feedback control of the treatment therapy and/or electrodepositioning. One or more sensors are attached to or implanted into aportion of a patient's body suitable for detecting a physical and/orchemical symptom or an important related symptom of the body. Thefeedback aspect of the present invention is discussed in further detailherein.

[0055] Although the invention will be described herein with reference tospinal cord stimulation (SCS) procedures, Cortical Surface Stimulation,and or Deep Brain Stimulation (DBS) it will be recognized that theinvention finds utility in applications other than SCS procedures,including other applications such as Peripheral Nerve or GangliaStimulation, Intra-Spinal Stimulation, Sacral Root Stimulation, orIntraventricular Cerebral Stimulation. In addition, the invention findsapplicability to SCS procedures where the lead is placed in theintrathecal or subdural space. The present invention may also beutilized to provide stimulation of various muscles of the body such asthe cardiac muscle. The invention also finds utility to drug therapywhere electrical components are replaced with conduits and catheters forconducting drug material to the therapy site. In this case, especially,the lead may be placed in the intrathecal or subdural space.

[0056]FIG. 2 is a cross-sectional view of spinal cord 12 at spinal bonelevel T-6 having an implanted lead 23A in accordance with a preferredembodiment of the present invention. Spinal cord 12 generally includeswhite matter 31, grey matter 33, and a surrounding dural sack 30. Asshown, lead 23A is implanted in the epidural space outside of dural sack30, but may alternatively be implanted in intrathecal spinal space orsubcortically beneath dura 30. Lead 23A has a curved shape to match theshape of dura 30. The curvature may be matched to each spinal level ormay be a general shape to approximately match all levels of spinal cord.Alternatively, lead 23A may be flat such that it “grips” the vertebralbone on its dorsal edges and is less prone to migration or rotation.Lead 23A has a dorsal side 125 away from spinal cord 12 and a ventralside 120 facing spinal cord 12.

[0057] FIGS. 2-4 show the average width, height and spacing of tissuecomponents at vertebral bone level T6. The dashed lines in these figuresindicate distances of one standard deviation from the mean. See J.Holsheimer et al., “MR Assessment of the Normal Position of the SpinalCord in the Spinal Cannal,” Am. J. Neuroradiology, Vol. 15, pp. 951-959(1994).

[0058] Referring still to FIG. 2, lead 23A has two lateral electrodecontacts 31 and 32 at opposite ends of lead 23A and a central electrodecontact 33 in the central portion of lead 23A. Lateral and centralelectrodes 31-33 may be anodes, cathodes or nonactive. Alternatively,any one or more of lateral and central electrodes 31-33 may be recordingelectrodes or drug delivery ports. Lead 23A is preferably able tocontrol the dorsal cerebral spinal fluid (CSF) width, even though it isplaced outside of dura. In accordance with the present invention, lead23A includes a position control mechanism capable of adjusting theposition of one or more of the lateral or central electrodes 31-33. Asshown, central electrode 33 is at a maximal distance dorsally fromspinal cord 12. A position control mechanism may adjust the distancebetween central electrode 33 and the spinal cord 12. In the embodimentof FIG. 2, the position control mechanism is in the form of a cavity 34within lead 23A which is able to expand and fill with fluid (controlledby a pump (not shown)) or other matter in the epidural space to reducethe separation between central electrode 33 and spinal cord 12. A pump(not shown) may be powered by signal generator 14 that also provides thestimulation energy for the electrodes at lateral and central electrodes31-33 and a signal for controlling the position control mechanism.Alternatively, position control mechanism may be adjusted using externalmeans and power such as a magnetic signal, a percutaneous needle or bulbon another component that can be pushed. Advantageously, centralelectrode 33 may be positioned such that the targeted neural tissue isstimulated with optimal efficacy and minimal side effects.

[0059] As shown in FIGS. 3 and 4, the position control mechanism maytake any number of embodiments for allowing movement of the electrodesand holding the electrodes in position. FIG. 3 illustrates a positioncontrol mechanism having metal bellows 35 and FIG. 4 illustrates aposition control mechanism having a piston 36. The bellows 35 of FIG. 3may alternatively be a threaded rod. A spring may be added to return theelectrode to a less extended position.

[0060] Further, the position control mechanism may control all or aselective group of electrodes. For example, one position controlmechanism may control a longitudinal or transverse row of electrodes.Alternatively, each electrode to be adjusted may have its own individualposition control mechanism.

[0061] The position control mechanism of the above embodiments ispreferably controlled by a position controller which is discussed infurther detail herein. The position control mechanism is preferablyadjustable such that it does not unduly depress neural tissue or hinderblood flow. Sensing feedback may be utilized, for example by amechanical measure within a lead or an ultrasound or other sensor togive information about the distance. Sensing feedback may also beutilized to automatically adjust the positioning of the electrodes toprovide optimum treatment therapy. Sensing feedback is discussed infurther detail herein.

[0062] FIGS. 5-9 disclose another group of embodiments of the presentinvention where electrodes are anchored to vertebral bones of the spinalcord. Alternatively, the electrodes may be implanted in the corticalbone of the skull. Electrodes may be positioned by drilling one or moreholes at preselected locations in the bone. Leads having one or moreelectrodes may then passed through the holes and positioned inside thevertebral canal/skull at optimal locations or distances from the targetneural tissue. Electrodes may then be selectively adjusted in positionafter the implant. The depth of the electrodes may then be adjusted toprovide the optimal stimulation therapy.

[0063] As shown in FIG. 5A, an electrode 40 at the end of a threadedhousing 43 is provided by drilling housing 43 into bone 42 surroundingspinal cord 12. For dorsal column stimulation, bone 42 is preferably thedorsal aspect of vertebral bone. The lead 23B is coupled to electrode 40and extends out through a top portion 41 of threaded housing 43. FIGS.5B-D illustrate exemplary embodiments of the top portion of housing 41to allow for engagement of various turning devices. FIG. 5B depicts acavity 45 to provide engagement of a screwdriver-like device to turnhousing 43 to adjust position of electrode 40 relative to spinal cord12. FIG. 5C depicts a similar device but providing engagement of aslotted screwdriver-like device. FIG. 5D depicts a hexagonal cavity 47for engagement of a hexagonal wrench-like device or percutaneous needle.Housing 43 preferably is threaded with a high pitch so that a relativelysmall turn provides relatively larger positioning of electrode 40relative to the spinal cord 12. This minimizes the problem of lead 23Bwrapping around housing 43.

[0064]FIG. 6 discloses another embodiment of the present inventionhaving a collar 50 screwed into bone 42. An inner housing 52 similar tothe housing 43 of FIG. 5 may be used to move electrode 40 relative tocollar 50. This embodiment allows adjustment of electrode 40 at timesafter the system has been implanted and is less affected by growth oftissue over housing 52 and collar 51 to limit subsequent turning ofhousing 52 relative to collar 51. FIG. 7 discloses another embodimentwhere collar 51 has an “O” ring 54 to hold housing 53 in position bypressure. Other means to lock housing 53 in position are also possible.

[0065] As shown in FIGS. 8 and 9, a plurality of electrodes may beprovided than can be selectively or collectively adjusted relative tospinal cord 12. These electrodes may also be provided in athree-dimensional configuration along spinal cord 12. Further, thoughelectrodes may be positioned closer to spinal cord 12, they preferablydo not break the dural sack 30 to avoid leakage 15. of CSF. FIG. 9 showsa ball and socket 905 or other swivel mechanism to allow turning ofhousing but not lead. Advantageously, placement of the lead through thevertebral bone avoids the problem of lead migration.

[0066] Alternatively, the lead may be implanted into the bone, asopposed to implant all the way through the bone, as illustrated in FIGS.36A-D. For example, FIG. 36A depicts a lead 5 implanted into the bonyaspects of the vertebral body. The lumbar spine is shown with the leadinserted into the pedicle 2 of the vertebral body 1 to stimulate nerveroots, particularly as the nerve roots 3 exit the spinal foramen 4. Thelead 5 is implanted by drilling a hole through the pedicle 2 (from theposterior) and into the vertebral body. The lead 5 may then be insertedinto the hole and fed to the end. Once in position, the lead 5 may beanchored at the posterior, bone entrance site using, for example, a burrcap. By keeping the lead hole medial and centered, the nerve roots canbe stimulated. The specific target nerve site may be selected by varyingthe placement of the lead relative to the vertebral bone. FIG. 36B showsan isometric drawing of pedicular placement for stimulation of the nerveroot as it exits the spinal foramen 4. Lead 5 is inserted into in theinferior portion of the vertebral pedicle 2 of the vertebral segment toenable stimulation of the dorsal root ganglion 6. By way of anotherexample, in FIG. 36C, a lead 5 placed in the superior lateral portion ofthe vertebral bone will enable stimulation of the spinal nerve 7 of thesegment superior. Advantageously, lead 5 may be placed so as to targetdesired neural tissue and avoid other tissue. In addition, lead 5 isanchored within the vertebral bone, thereby avoiding the risk of leadmigration and avoiding compression of nerve tissue common in knowntechniques.

[0067] In addition, lead 5 may be implanted in any other bone areas thatare proximal to targeted neural tissue. An example of placement totarget other neural tissue is illustrated in FIG. 36C. This Figureillustrates placement for stimulation of the ganglia (8) of thesympathetic trunk. The hole for lead 5 is angled more lateral and madedeeper up to the wall of the vertebral body 1. FIG. 36D is an isometricview of the same lead placement shown in FIG. 36C. The hole in thevertebae begins at the posterior and is extended down the pedicle 2,into the veretbral body 1, toward the ganglion 8, but not through thewall of the vertebral body. This method allows stimulation of deeptissues without distrupting soft tissue. Again the lead could beanchored in the posterior bone by a burr hole cap or other means. Lead 5of FIGS. 36A-D may be adjustable similar to those of FIGS. 5-9.

[0068] The advantages of fixing a lead to a vertebral bone may also beimplemented in Cortical Brain Stimulation applications. FIG. 38Adiscloses another embodiment where one or more motor cortex electrodes(MCE) 308 are implanted into the skull of a patient for stimulationand/or recording of the cortex via contact with the dura. As shown inFIG. 38B, MCE 308 may be screwed using a burr hole ring 309 and screw310 within the skull 311 of a patient using known techniques.Advantageously, the present embodiment enables several MCEs 308 to beplaced to allow flexibility in choosing the best stimulation. A MCEtargeting grid (FIG. 38C) could be constructed of a material such as,for example, CuSO₄, SO that the hole locations are visible undermagnetic resonance imaging (MRI). Placement of the MCE 308 within theskull 311 allows for more accurate placement of the MCEs 308 and avoidsthe problem of lead migration. In addition, screw 310, referring to FIG.38B, can be advanced or retracted to ensure an optimal contact betweenthe electrode 308 and dura 314 to maximize stimulation effect whileminimizing mechanical deformation of dura and cortex. Further, lessinvasive surgical procedure is required, thereby minimizing the risk ofdamage to the dura 314. Such a configuration of MCEs 308 may be used forcortex stimulation for any number of disorders, including but notlimited to, pain, epilepsy, anxiety/physiological disorders, andmovement disorders.

[0069] In addition to minimizing lead migration, the present inventionalso allows the lead to be positioned to be optimally closer to thedesired treatment area. The embodiments discussed herein illustrate thevarious techniques that may be used to non-invasively position andre-position therapy delivery elements after they have been surgicallyimplanted. Positioning of the treatment delivery elements may belaterally in any direction or toward or away from the desired treatmentsite. FIG. 10 discloses an embodiment of the present invention where aballoon-like structure 60 is implemented on a dorsal side of a paddlelead 62. The balloon may also be positioned on a lateral side of paddlelead 62. Paddle lead 62 may have one or more electrodes 64. Lead 62 maybe positioned closer to spinal cord 12 by filling of balloon 60 with afluid. In the event that it is desired that lead 62 be moved away fromspinal cord 12, fluid may be removed from 60. FIGS. 12A-B depict otherembodiments wherein a plurality of balloons are implemented to allowmore selective adjustment of the electrodes 64 relative to the spinalcord 12. These or other balloons may also be positioned on the sides ofthe lead so that the lead may be positioned from right to left. FIGS.13A-B illustrate another embodiment wherein balloon 90 includes a rigidor semi-rigid dorsal component 92. FIGS. 14A-B illustrate yet anotherembodiment wherein balloon 94 includes a rigid or semirigid dorsalcomponent 98 having a hinge 96 to allow component to form to the shapeof the dorsal aspect of the patient's vertebral cannal when balloon 94is filled with fluid.

[0070] The amount of fluid in the balloon of FIGS. 12A-B, 13A-B and14A-B may be controlled by a device similar to the position mechanism ofFIG. 2. These balloons may be made of an elastic or inelastic material.FIG. 11 illustrates an alternative technique for adding or removingfluid to balloon 60. A septum 70 is provided just underneath the skin 72of the patient. A noncoring needle 74 may be utilized to deliver orremove additional fluid to a reservoir 76 via septum 70. The delivery orremoval of fluid may then be controlled to any one of the balloons viatube 78 as needed. FIG. 15 depicts another embodiment wherein a separatereservoir and septum pair is provided for each of two balloons. In thecase of three balloons, three reservoir/septum pairs may be provided.FIG. 16 discloses yet another embodiment wherein a single septum 80 isprovided but reservoirs 82 and 84 may transfer fluid between each other.Each reservoir has an associated bulb or depression mechanism 86A-B thatcan be accessed externally by pressing on the skin 72 of the patient.Each depression mechanism includes a spring 87 and ball 88 assembly. Forexample, by depressing mechanism 86B, fluid may be delivered from area79B of reservoir 84 to reservoir 82 via tube 89. Also, when bulb 86A isdepressed, fluid in area 79A is delivered from reservoir 82 to reservoir84. Also, a separate reservoir may be utilized to add or remove fluidfrom reservoirs 82 and 84. Such systems are known in the art for aninflatable urinary sphincter and an inflatable penile erector. Thesystem may allow the patient to make these adjustments as needed.

[0071] FIGS. 17A-D disclose other embodiments whereby the electrodes areadjusted using gliders GL1 and GL2. As shown in FIGS. 17A-B, gliders GL1and GL2 are constrained to move along a groove 115 transverse to ventralcomponent 120 of lead as shown in FIG. 17C. One or more pulley systemswith wires may be utilized to move gliders GL1 and GL2 individually orcollectively. Referring back to FIGS. 17A-B, gliders GL1 and GL2 areattached to ends of rigid arms L1 and L4 respectively. The opposite endsof arms L1 and L4 are attached to joints J1 and J4 respectively whichare fixed relative to a semi-rigid or flexible dorsal component 110.Joints J1 and J4 are also connected to ends of rigid arms L2 and L3respectively. Opposite ends of arms L2 and L3 are attached to joints S2and S1 respectively which are fixed relative to ventral component 120 ofthe lead. The entire assembly may be encased within a membrane-likehousing 130 to prevent connective tissue in-growth. Ventral component120 may be positioned closer to spinal cord 12 by moving gliders GL1 andGL2 relative to groove 115. As shown in FIG. 17B, ventral component 120may be closest to spinal cord when gliders GL1 and GL2 are positionedunder the joints J1 and J4. A glider may also be positioned to moveparallel to spinal cord 12 along the lead. As shown in FIGS. 17D-E, anynumber of glider geometries may be utilized to adjust to adjust theposition of ventral component 120.

[0072] FIGS. 18A-C disclose yet other embodiments whereby the electrodesare adjusted using movable, flexing wires. As shown in FIG. 18A, ventralcomponent 120 of a lead is positioned relative a semi-rigid dorsalcomponent 125. Wires 137 are positioned at opposite sides of theassembly. As shown in FIG. 18B, wire 137 is implemented within a sheath131 whose end is fixed to ventral component 120. The distal end of wire137 is anchored at point P1 and is also fixed relative to ventralcomponent 120 of the lead. Wire 137 may be pushed or pulled along sheath131 causing it to bend or straighten along its body 138. As wire 137 ispushed toward point P1, it bends causing the body 138 to exert pressureagainst dorsal component 125 and end P1 to exert pressure againstventral component 120. Wire 137 thus causes a portion of ventralcomponent 120 to move away from dorsal component 125 thereby causing aportion of the lead to expand and position electrodes E1 on that portionto move closer to the spinal cord 12. When wire 137 is pulled back awayfrom point P1, wire 137 reduces its pressure exerted on dorsal andventral components 120 and 125, thereby allowing a portion of the leadto reduce its thickness and electrodes E1 on that portion to move awayfrom spinal cord 12. As shown in FIG. 18C, a plurality of wireassemblies may be incorporated to adjust the position of lead 120relative to the spinal cord 12 along various points.

[0073]FIG. 19 discloses yet another embodiment whereby the electrodesare adjusted using a piston C1 and a spring S1. Piston C1 may be movedto push or pull ventral component 120 relative to semi-rigid dorsalcomponent 125. Spring S1 has a preset tension to return ventralcomponent 120 to a default position once the pressure exerted by pistonC1 is removed. As in the previously discussed embodiments, more than onepiston/spring assembly may be located laterally as well as along thelength of lead. Alternatively, bellows may be used in place of piston C1and spring S1.

[0074]FIG. 20 discloses yet another embodiment whereby the lead isadjusted using a gear mechanism. A gear 160 may be rotated about an axisbut is held in a fixed position relative to either semi-rigid dorsalcomponent 125 or ventral component 120. Slidable elements 165 haveramped surfaces with teeth that interact with gear 160. The upperelement 165 is coupled to slide relative to semi-rigid dorsal component125 and the lower slidable element is coupled to slide relative toventral component 120. As gear rotates, slidable elements 165 are movedin opposite directions relative to each other. With a clockwise turn ofgear 160, lower element 165 slides to the left and upper element slidesto the right. The elements thereby push ventral component 120 away fromsemi-rigid dorsal component 125 and toward spinal cord 12. Two or moregears may be implemented to minimize asymmetry in lead thickness.

[0075] As shown in FIGS. 21A-C, a gear mechanism may be incorporatedinto any number of embodiments. FIG. 21A discloses a toggle mechanismhaving one gear 170 attached to a component with an associated left orright wing 171. As gear 170 is rotated, wings 171 are rotatedaccordingly. As shown in FIG. 21B, rotation of wings 171counter-clockwise pushes up against semi-rigid dorsal component 125causing that portion of lead to increase its thickness, thereby movingthat portion of ventral component 120 toward spinal cord 12. Gear 170may be controlled by slidable toothed elements 175. As shown in FIG.21C, there may be two gears (one is shown), each connected to asingle-sided wing 171 a or 171 b to change the lateral lead thicknessindependently. Wings 171 a-b may also have transverse extensions 173 a-b(parallel to spinal cord 12) to push against dorsal component 125.

[0076] The lead may be configured in any number of ways using anycombination of the above-detailed structures. For example, FIGS. 22 and23 illustrate that two or more of the above-detailed techniques (such aswings, flexing wires and/or springs) may be combined to provide thedesired control of lead thickness.

[0077]FIG. 24 illustrates yet another embodiment of a lead according toa preferred embodiment of the present invention for use in SCS therapy.This design allows movement of electrodes toward or along spinal nerveroots within the spinal canal as they pass caudally and laterally towardtheir respective foraminae (exits from the vertebral bones). Inaccordance with known techniques, a Tuohy needle 314 is utilized andpositioned near the spinal cord. Lead body 318 is inserted through thelumen 316 of Tuohy needle 314 and positioned near the spinal cord 12. Aproximal end (not shown) of lead body 318 is ultimately to be connectedto a source device (not shown) which may be signal generator 14 of FIG.1, in the case of electrical stimulation, or a drug pump in the case ofdrug therapy. Lead 318 is provided with a distal tip 320 that may becompacted for insertion and unfolded after it has been positionedappropriately within the body. Distal tip 320 includes a central portion322 and at least one span 324 depending therefrom. Span 324 is comprisedof a flexible, insulative material, such as polyurethane or siliconerubber. The term “flexible” as used herein refers to both resilient andnon-resilient materials. Central portion 322 may have a generallysemi-circular cross-section as shown, or may be flat such as in the caseof a paddle lead (exemplified in FIG. 26). Affixed to a surface of spans324 and to central portion 322 is a series of electrodes 326. Inaccordance with the invention, lead 320 may be configured into a compactinsertion position for ease of insertion through lumen 316 of Tuohyneedle 314.

[0078] Once in position near the implant site, lead tip 320 may bedeployed out of Tuohy needle 314, as shown in FIG. 24. In the embodimentof FIG. 24, spans 324 are semirigid and tend to span out at apredetermined angle. To optimally position lead spans 324 along spinalnerve roots, lead 320 may be pulled back into the Tuohy needle 314. Asit moves back, spans 324 will tend to move laterally as well asdownward, along the path of a nerve root. Needle 314 may be replaced bya sheath component for adjustments after implant. In the embodiment ofFIG. 25, spans 324 may be rigid or flaccid and are coupled to a lever330 capable of adjusting the lateral displacement of spans 324. Lever330 extends from spans 324 to body struts 319. Struts 319 pass inside oralong lead body 318 to controllers (not shown). As lever 330 is movedtoward distal end of lead 320 by pushing on struts 319, spans 324 aredisplaced further in a lateral direction. Lever 330 may be coupled to acontrol mechanism such that spans 324 may be re-positioned at futuretimes to provide optimal treatment therapy. FIG. 26, discloses anotherembodiment of a paddle lead 420 having spans 424 which can rotate tolateral positions. FIGS. 27A-B disclose yet another embodiment of apaddle lead 520 capable of extending electrodes laterally to track alongspinal nerves. Such a mechanism may be similar to that of a carantenna-like device whereby a rigid or semi-rigid wire may extendlaterally from lead 520. An internal stylet 521 may be utilized toadjust the length of the span 522. As shown in FIG. 27A, when stylet 521is inserted within the lead 520 and is closest to the lead tip, the span522 is retracted and inside lead 520. As stylet 521 is pulled to theleft, span 522 is directed out as shown in FIG. 27B to direct electrodes523 laterally away from lead 520. This embodiment may be incorporatedwith the embodiments of FIGS. 24-26 and 27A-B to allow adjustment of theextent of the lateral displacement as well as the angle of the lateraldisplacement.

[0079] The above embodiments illustrate various techniques for allowingtherapy delivery elements to be positioned during and/or after implantto effectively provide treatment therapy to the targeted area of thespinal cord or brain. Further, relief may be provided with a loweramplitude, and motor or other undesirable side effects may be minimized.As exemplified in the above embodiments, any number of techniques may beutilized.

[0080] The present invention may also be utilized within the brain toprovide electrical stimulation as well as delivery of one or more drugs.The present invention may be implemented within a system as disclosed inU.S. patent application entitled “Techniques For Selective Activation OfNeurons In The Brain, Spinal Cord Parenchyma, and Peripheral Nerve,”invented by Mark Rise and Mike Baudino, which is incorporated herein byreference in its entirety. Treatment therapy may be provided to thebrain to treat any number of diseases. Sometimes, the disease willprogress to another part of the brain. The present invention may therebybe used to advance the electrodes to a different part of the brain. Forexample, electrodes and/or catheters may be implanted within the brainto treat tremor. Later, it may be desirable to address symptoms ofakinesia or bradykinesia which were not clearly present when thetreatment device was originally implanted. The present invention maythereby extend or shorten the leads to effect different areas of thebrain tissue. Alternatively, leads may be adjusted to achieve optimalpositioning.

[0081] For example FIG. 37A depicts a lead 37 composed of concentrictubes 38, preferably metal such as platinum. These tubes may be coatedwith a polymer except for the distal end portions 39 that serve as theelectrodes. The conductive wires 40 carrying energy to the electrodesare in the interior of the concentric tubes. Optionally, the most distalelectrode end 41 may be a small recording microelectrode to help assistin the actual placement of the lead. As shown in FIG. 37B, the lead 37may be implanted within the brain under known techniques. A pusher 42may be placed into the lead through the proximal portion to make thelead 37 stiff during the introduction phase and/or to provide amechanism to push the concentric tubes 38 out and away from the outertube or cannula 43. After implant, the outer cannula 43 may optionallybe removed.

[0082] The present invention may be operated as an open-loop controlledsystem. In an open-loop system, the physician or patient may at any timemanually or by the use of pumps or motorized elements adjust thepositioning of the electrodes in situ and change stimulation parameters.However, this subsequent position adjustment would be independent of anyintended changes in stimulation effect or side-effects the patient maybe experiencing, and an iterative procedure may be necessary.

[0083] Optionally, the present invention may incorporate a closed-loopcontrol system which may automatically adjust (1) the positioning of theelectrodes in response to a sensed condition of the body such as aresponse to the treatment therapy; and/or (2) the electrical stimulationparameters in response to a sensed symptom or an important relatedsymptom indicative of the extent of the disorder being treated. Under aclosed-loop feedback system to provide automatic adjustment of thepositioning of the electrodes, a sensor 130A (FIG. 28) that senses acondition of the body is preferably utilized. For example, sensor 130Amay detect patient position to discern whether the patient is lying downor is in an erect position. Typically, spinal cord stimulation becomesstrong when the patient lies down due to the spinal cord moving in adorsal direction toward the lead. In such a situation, the positioncontrol mechanism may adjust electrodes to move away from spinal cord.Alternatively, one or more recording electrodes may be utilized toprovide feedback.

[0084] More detailed description of sensor 130A, other examples ofsensors and the feedback control techniques are disclosed in U.S. Pat.No. 5,716,377 entitled “Method of Treating Movement Disorders By BrainInfusion,” issued on Feb. 10, 1998 and assigned to Medtronic, Inc.,which is incorporated herein by reference in its entirety.

[0085] Referring to FIG. 28, the output of sensor 130A is coupled by acable 132 comprising conductors 134 and 135 to the input of analog todigital converter 140A. Alternatively the output of the sensor 130Acould communicate through a “body bus” communication system as describedin U.S. Pat. No. 5,113,859 (Funke), assigned to Medtronic which isincorporated by reference in its entirety. Alternatively, the output ofan external feedback sensor 130A would communicate with signal generator14 through a telemetry down-link. The output of the analog to digitalconverter 140A is connected to a microprocessor 200 via terminals EF2BAR and EF3 BAR. The sensor signals may then be stored in a memorydevice such as a Random Access Memory (RAM) 102 a. Such a configurationmay be one similar to that shown in U.S. Pat. No. 4,692,147 (“'147patent”) except that before converter 140A is connected to theterminals, the demodulator of the '147 patent (identified by 101) wouldbe disconnected. Microprocessor 200 may then be coupled to a positioncontroller 201.

[0086] For some types of sensors, microprocessor 200 and analog todigital converter 140A would not be necessary. The output from sensor130A can be filtered by an appropriate electronic filter in order toprovide a control signal for position controller. An example of such afilter is found in U.S. Pat. No. 5,259,387 “Muscle Artifact Filter,Issued to Victor de Pinto on Nov. 9, 1993, incorporated herein byreference in its entirety.

[0087] Closed-loop control of position controller can be achieved by amodified form of the ITREL II signal generator. Referring to FIG. 30,the output of the analog to digital converter 140A is connected tomicroprocessor 200 through a peripheral bus 202 including address, dataand control lines. Microprocessor 200 processes the sensor data indifferent ways depending on the type of transducer in use.Microprocessor may adjust the position of the electrodes in response tothe sensor signal information provided by sensor 130A. The type ofcontrol provided depends upon the type of position controller utilizedand the mechanism utilized (discussed above) to position the electrodes.In the case where position controller relies on electrical energy tocause mechanical movement (e.g., pumps, motors and the like) or ispurely electrical control, microprocessor 200 or a second microprocessormay serve as the position controller. In the case where positionrequires mechanical control, an appropriate controlling device is used.For example, in the embodiment of FIGS. 10-16 where position iscontrolled by filling a balloon with fluid, position controller may beincorporated within a reservoir system for holding the fluid outside thelead's balloon. Torque from percutaneous instruments that engages in amechanical component may also be used.

[0088] The present invention may also incorporate a closed-loop feedbacksystem to provide automatic adjustment of the electrical stimulationtherapy. Such is system is disclosed in U.S. Pat. No. 5,792,186 entitled“Method and Apparatus of Treating Neurodegenerative Disorders byElectrical Brain Stimulation,” and assigned to Medtronic, Inc., which isincorporated herein by reference in its entirety. The system mayincorporate the same sensor 130A discussed above or one or moreadditional sensors 130 to provide feedback to provide enhanced results.Sensor 130 can be used with a closed loop feedback system in order toautomatically determine the level of electrical stimulation necessary toprovide the desired treatment. For example, to treat motion disordersthat result in abnormal movement of an arm, sensor 130 may be a motiondetector implanted in the arm. More detailed description of sensor 130,other examples of sensors and the feedback control techniques aredisclosed in U.S. Pat. No. 5,716,377 entitled “Method of TreatingMovement Disorders By Brain Infusion,” issued on Feb. 10, 1998 andassigned to Medtronic, Inc., which is incorporated herein by referencein its entirety. Other such sensors are also disclosed in U.S. Pat. Nos.5,683,422; 5,702,429; 5,713,923; 5,716,316; 5,792,186; 5,814,014; and5,824,021.

[0089] Closed-loop electrical stimulation can be achieved by a modifiedform of the ITREL II signal generator which is described in FIG. 30. Theoutput of the analog to digital converter 206 is connected to amicroprocessor 200 through a peripheral bus 202 including address, dataand control lines. Microprocessor 200 processes the sensor data indifferent ways depending on the type of transducer in use. When thesignal on sensor 130 exceeds a level programmed by the clinician andstored in a memory 204, increasing amounts of stimulation will beapplied through an output driver 224. For some types of sensors, amicroprocessor and analog to digital converter will not be necessary.The output from sensor 130 can be filtered by an appropriate electronicfilter in order to provide a control signal for signal generator 14. Anexample of such a filter is found in U.S. Pat. No. 5,259,387 “MuscleArtifact Filter, Issued to Victor de Pinto on Nov. 9, 1993, incorporatedherein by reference in its entirety.

[0090] Still referring to FIG. 30, the stimulus pulse frequency iscontrolled by programming a value to a programmable frequency generator208 using bus 202. The programmable frequency generator 208 provides aninterrupt signal to microprocessor 200 through an interrupt line 210when each stimulus pulse is to be generated. The frequency generator 208may be implemented by model CDP1878 sold by Harris Corporation. Theamplitude for each stimulus pulse is programmed to a digital to analogconverter 218 using bus 202. The analog output is conveyed through aconductor 220 to an output driver circuit 224 to control stimulusamplitude. Microprocessor 200 also programs a pulse width control module214 using bus 202. The pulse width control 214 provides an enablingpulse of duration equal to the pulse width via a conductor. Pulses withthe selected characteristics are then delivered from signal generator 14to the lead to the target locations of spinal cord 12.

[0091] Microprocessor 200 executes an algorithm shown in FIGS. 31-5 toprovide stimulation with closed loop feedback control. At the time thestimulation signal generator 14 or an alternative device havingstimulation and/or infusion functions is implanted, the clinicianprograms certain key parameters into the memory of the implanted devicevia telemetry. These parameters may be updated subsequently as needed.Step 400 in FIG. 31 indicates the process of first choosing whether theneural activity at the stimulation site is to be blocked or facilitated(step 400(1)) and whether the sensor location is one for which anincrease in the neural activity at that location is equivalent to anincrease in neural activity at the stimulation target or vice versa(step 400(2)). Next the clinician must program the range of values forpulse width (step 400(3)), amplitude (step 400(4)) and frequency (step400(5)) which signal generator 14 may use to optimize the therapy. Theclinician may also choose the order in which the parameter changes aremade (step 400(6)). Alternatively, the clinician may elect to usedefault values.

[0092] The algorithm for selecting parameters is different depending onwhether the clinician has chosen to block the neural activity at thestimulation target or facilitate the neural activity. FIGS. 31-35 detailthe steps of the algorithm to make parameter changes.

[0093] The algorithm uses the clinician programmed indication of whetherthe neurons at the particular location of the stimulating electrode areto be facilitated or blocked in order to decide which path of theparameter selection algorithm to follow (step 420, FIG. 32). If theneuronal activity is to be blocked, signal generator 14 first reads thefeedback sensor 130 in step 421. If the sensor values indicate theactivity in the neurons is too high (step 450), the algorithm in thisembodiment first increases the frequency of stimulation in step 424provided this increase does not exceed the preset maximum value set bythe physician. Step 423 checks for this condition. If the frequencyparameter is not at the maximum, the algorithm returns to step 421through path 421A to monitor the feed back signal from sensor 130.

[0094] If the frequency parameter is at the maximum, the algorithm nextincreases the pulse width in step 426 (FIG. 33), again with therestriction that this parameter has not exceeded the maximum value aschecked for in step 451 through path 423A. Not having reached maximumpulse width, the algorithm returns to step 421 to monitor the feedbacksignal from sensor 130. Should the maximum pulse width have beenreached, the algorithm next increases amplitude in a like manner asshown in steps 427 and 428. In the event that all parameters reach themaximum, a notification message is set in step 429 to be sent bytelemetry to the clinician indicating that therapy delivery device 14 isunable to reduce neural activity to the desired level.

[0095] If, on the other hand, the stimulation electrode is placed in alocation which the clinician would like to activate to alter thesymptoms of the neurological disorder, the algorithm would follow adifferent sequence of events. In the preferred embodiment, the frequencyparameter would be fixed at a value chosen by the clinician tofacilitate neuronal activity in step 430 (FIG. 34) through path 420A(FIG. 32). In steps 431 and 432 the algorithm uses the values of thefeedback sensor to determine if neuronal activity is being adequatelycontrolled. In this case, inadequate control indicates that the neuronalactivity of the stimulation target is too low. Neuronal activity isincreased by first increasing stimulation amplitude (step 434) providedit doesn't exceed the programmed maximum value checked for in step 433.When maximum amplitude is reached, the algorithm increases pulse widthto its maximum value in steps 435 and 436 (FIG. 35). A lack of adequatealteration of the symptoms of the neurological disorder, even thoughmaximum parameters are used, is indicated to the clinician in step 437.After steps 434, 436 and 437, the algorithm returns to step 431 throughpath 431A, and the feedback sensor again is read.

[0096] It is desirable to reduce parameter values to the minimum levelneeded to establish the appropriate level of neuronal activity in thespinal cord. Superimposed on the algorithm just described is anadditional algorithm to readjust all the parameter levels downward asfar as possible. In FIG. 31, steps 410 through 415 constitute the methodto do this. When parameters are changed, a timer is reset in step 415.If there is no need to change any stimulus parameters before the timerhas counted out, then it may be possible due to changes in neuronalactivity to reduce the parameter values and still maintain appropriatelevels of neuronal activity in the target neurons. At the end of theprogrammed time interval, signal generator 14 tries reducing a parameterin step 413 to determine if control is maintained. If it is, the variousparameter values will be ratcheted down until such time as the sensorvalues again indicate a need to increase them. While the algorithms inFIGS. 31-35 follow the order of parameter selection indicated, othersequences may be programmed by the clinician.

[0097] The stimulation might be applied periodically during the periodof stimulation/infusion either routinely or in response to sensor orpatient generated demand. Alternatively, in the case of simultaneousstimulation and drug therapy, stimulation could be applied continuouslywith infusion occurring periodically. Patient activation of eitherinfusion or stimulation may occur as a result of an increase in symptomsbeing experienced by the patient. Alternatively, the infusion of anagent to activate a neuronal population might be alternated withapplication of electrical stimulation of that same population.

[0098] Advantageously, the present invention may be used to selectivelyposition stimulation electrodes optimally closer to the targeted neuraltissue to more effectively deliver a desired treatment therapy. Thoseskilled in that art will recognize that the preferred embodiments may bealtered or amended without departing from the true spirit and scope ofthe invention, as defined in the accompanying claims. For example, thepresent invention may also be implemented within a drug delivery systemand/or may be implemented to provide treatment therapy to other parts ofthe body such as the brain, nerves, muscle tissue, or neural ganglia.Further, the various embodiments of the present invention may beimplemented within a percutaneous lead or a paddle lead.

We claim:
 1. A method for providing treatment therapy to a targeted tissue by means of a therapy delivery device and at least one therapy delivery element coupled to the therapy delivery device, the method comprising the steps of: (a) implanting at least one lead having at least one therapy delivery element so that the therapy delivery element lies in communication near the targeted tissue; (b) coupling a proximal end of the lead to the therapy delivery device; (c) operating the therapy delivery device to provide treatment therapy to the targeted tissue via the implanted therapy delivery element; and (d) adjusting, at any time after the step of implanting, the position of at least one implanted therapy delivery element relative to the targeted tissue.
 2. A method as claimed in claim 1 , wherein the targeted tissue is neural tissue.
 3. A method as claimed in claim 2 , wherein the neural tissue is in the spinal cord.
 4. A method as claimed in claim 2 , wherein the neural tissue is in the brain.
 5. A method as claimed in claim 1 , wherein the targeted tissue is neural ganglia.
 6. A method as claimed in claim 1 , wherein the targeted tissue is muscle tissue.
 7. A method as claimed in claim 1 , wherein the therapy delivery device is a signal generator and the therapy delivery element is an electrode.
 8. A method as claimed in claim 1 , wherein the therapy delivery device is a pump and the therapy delivery element is a catheter.
 9. A method as claimed in claim 1 , wherein the step of adjusting includes the step of sensing a condition of a response to the treatment therapy and the step of adjusting is performed in response to the step of sensing.
 10. A method as claimed in claim 1 , further comprising the steps of: (e) sensing a symptom indicative of a condition to be treated and generating a sensor signal; and (f) regulating the operation of the signal generator in response to the sensor signal.
 11. A method as claimed in claim 9 , further comprising the steps of: (e) sensing a symptom indicative of a condition to be treated and generating a sensor signal; and (f) regulating the operation of the signal generator in response to the sensor signal.
 12. A method as claimed in claim 1 , wherein the step of adjusting includes the step of positioning the electrode laterally from the lead.
 13. A method as claimed in claim 1 , wherein the step of adjusting includes the step of positioning the electrode from the lead toward or away the targeted tissue.
 14. A system for providing treatment therapy to targeted tissue comprising in combination: (a) a therapy delivery device; (b) at least one therapy delivery element coupled to the therapy delivery device for providing treatment therapy to the targeted tissue; and (c) at least one position control mechanism coupled to at least one of the therapy delivery elements for adjusting, at any time after implanting the therapy delivery elements, the position of the therapy delivery element relative to the targeted tissue.
 15. A system of claim 14 , wherein the therapy delivery device is a signal generator and the therapy delivery element is an electrode.
 16. A system of claim 14 , wherein the therapy delivery device is a pump and the therapy delivery element is a catheter.
 17. A system of claim 14 , further comprising: (d) a first sensor for generating a first sensor signal related to a condition of a body; and (e) position controller for adjusting the position of at least one of the therapy delivery elements in response to the first sensor signal.
 18. A system of claim 17 , wherein the sensor senses the body's response to the treatment therapy.
 19. A system of claim 14 , further comprising: (d) a first sensor for generating a second sensor signal indicative a condition to be treated; and (e) control means for regulating the operation of the therapy delivery device in response to the first sensor signal.
 20. A system of claim 17 , further comprising: (f) a second sensor for generating a second sensor signal indicative a condition to be treated; and (g) control means for regulating the operation of the therapy delivery element in response to the second sensor signal.
 21. A system of claim 14 , wherein the therapy delivery elements are part of a paddle lead.
 22. A system of claim 14 , wherein the therapy delivery elements are part of a paddle lead having at least one cavity for holding fluid, wherein a change in fluid within the lead would direct at least one of the therapy delivery elements of the lead toward or away from targeted tissue.
 23. A system of claim 14 , wherein the therapy delivery elements are part of a paddle lead having at least one bellows, wherein expansion or compression of the bellows would direct at least one of the therapy delivery elements of the lead toward or away from targeted tissue.
 24. A system of claim 14 , wherein the therapy delivery elements are part of a paddle lead having at least one piston, wherein expansion or compression of the piston would direct at least one of the therapy delivery elements of the lead toward or away from targeted tissue.
 25. A system of claim 14 , wherein the therapy delivery elements are part of a paddle lead having at least one piston and at least one spring, wherein expansion or compression of the piston or spring would direct at least one of the therapy delivery elements of the lead toward or away from targeted tissue.
 26. A system of claim 14 , wherein the therapy delivery elements are part of a paddle lead having a dorsal side and further comprising: (d) at least one inflatable balloon-like member attached to a dorsal side or a lateral side of the paddle lead and capable of being filled with fluid, wherein the addition or removal of fluid from at least one of the balloon-like members would direct at least one of the therapy delivery elements of the lead relative targeted tissue.
 27. A system of claim 26 , wherein the balloon-like member has one or more areas of inelastic material.
 28. A system of claim 27 , wherein the dorsal component has a hinge coupling two relatively rigid members.
 29. A system of claim 14 , wherein the electrodes are part of a paddle lead further comprising: (d) at least one glider means attached the paddle lead capable of positioning at least a portion of the paddle lead relative to the targeted tissue.
 30. A system of claim 14 , wherein the electrodes are part of a paddle lead further comprising: (d) at least one bendable wire means attached to the paddle lead capable of positioning at least a portion of the paddle lead relative to the targeted tissue.
 31. A system of claim 14 , wherein the electrodes are part of a paddle lead further comprising: (d) at least one gear mechanism attached to the paddle lead capable of positioning at least a portion of the paddle lead relative to the targeted tissue.
 32. A system of claim 14 , wherein the therapy delivery elements are part of an implantable lead and wherein the lead has: i. an elongate central portion; and ii. at least one extendable member having an end, the extendable member depending from the central portion and being adapted to assume a compact position, in which the end is disposed in close proximity to the central portion, and an extended position, in which the end is disposed at a location distal from the central portion, wherein the therapy delivery elements are positioned at least on the extendable member.
 33. An implantable lead for providing therapy to a body comprising: (a) an elongate central portion; (b) at least one extendable member having an end, the extendable member depending from the central portion and being adapted to assume a compact position, in which the end is disposed in close proximity to the central portion, and an extended position, in which the extendable member is disposed at an angle laterally from the central portion; and (c) at least one therapy delivery element disposed on the extendable member for delivering therapy to the body.
 34. The implantable lead according to claim 33 , wherein the span incorporates a resilient material to urge the span toward the extended position.
 35. The implantable lead according to claim 33 , wherein the lead is a paddle lead.
 36. The implantable lead according to claim 33 , wherein the extendable member may be elongated outwardly from the central portion to position the therapy delivery element toward or away from targeted tissue.
 37. The implantable lead according to claim 33 , wherein the extendable member includes a lever to adjust the angle of the extendable member.
 38. An implantable lead for providing therapy to a body comprising: (a) an elongate central portion; and (b) at least one extendable member having an end, the extendable member depending from the central portion and being adapted to assume a compact position, in which the end is disposed in close proximity to the central portion, and an extended position, in which the end is disposed at a location distal from the central portion; (c) at least one therapy delivery element disposed on the extendable member for delivering therapy to the body; (d) a lever coupled near the end of the extendable member and the central portion capable of selectively adjusting the direction of extension of the extendable member relative to the central portion.
 39. The implantable lead according to claim 38 , wherein the lead is a paddle lead.
 40. The implantable lead according to claim 38 , wherein the extendable member may be elongated outwardly from the end to direct the therapy delivery element toward or away from targeted tissue.
 41. A system for providing neurostimulation therapy to targeted tissue comprising in combination: (a) a signal generator; (b) at least one housing member implantable within a bone near the targeted tissue and adjustable relative to the bone; and (c) at least one electrode coupled to said signal generator and attached to a distal end of the housing member for providing electrical stimulation to the targeted tissue.
 42. A system of claim 41 , further comprising (d) a collar implantable within a bone near the neural tissue, and wherein the housing member is insertable within the collar and is adjustable relative to the collar.
 43. An implantable paddle-like lead for providing treatment therapy to targeted tissue of a body comprising: (a) a middle portion having at least one central therapy delivery element on a ventral side; (b) at least two end portions, each end portion having at least one end therapy delivery element on the ventral side; and (c) a fluid reservoir portion along the middle portion capable of receiving fluid and expanding the middle portion such that the central therapy delivery element is positioned away from a dorsal side of the lead.
 44. An implantable paddle-like lead for providing treatment therapy to targeted tissue of a body comprising: (a) a middle portion having at least one central therapy delivery element on a ventral side; (b) at least two end portions, each end portion having at least one end therapy delivery element on the ventral side; and (c) a piston coupling the front side and a back side of the lead capable of expanding the middle portion such that the central therapy delivery element is positioned away from a dorsal side of the lead.
 45. An implantable paddle-like lead for providing treatment therapy to targeted tissue of a body comprising: (a) a middle portion having at least one central therapy delivery element on a ventral side; (b) at least two end portions, each end portion having at least one end therapy delivery element on the ventral side; and (c) at least one bellows coupling the front side and a back side of the lead capable of expanding the middle portion such that the central therapy delivery element is positioned away from a dorsal side of the lead.
 46. An implantable paddle-like lead for providing treatment therapy to targeted tissue of a body comprising: (a) a ventral side having at least one therapy delivery elements; (b) a dorsal side opposite the front side; (c) at least one balloon-like member attached to the back side of the lead, the balloon-like member capable of expanding by receiving a fluid, whereby expansion of the balloon-like member resulting in positioning at least one of the therapy delivery elements closer to or further from the targeted tissue.
 47. An implantable paddle-like lead of claim 46 , wherein the balloon-like member has a relatively rigid component along a dorsal side of the member.
 48. An implantable paddle-like lead of claim 47 , wherein the relatively rigid component has a hinge coupling two relatively rigid members.
 49. An implantable paddle-like lead for providing treatment therapy to targeted tissue of a body comprising: (a) a ventral side having at least one therapy delivery elements; (b) at least one glider mechanism attached to the ventral side of the lead capable of movement; and (c) a membrane covering the glider means, whereby movement of the glider mechanism results in lead expansion and positioning of at least one of the therapy delivery elements closer to or further from the targeted tissue.
 50. An implantable paddle-like lead for providing treatment therapy to targeted tissue of a body comprising: (a) a ventral side having at least one therapy delivery elements; (b) at least one flexible wire means attached to the ventral side of the lead capable of flexing; and (c) a membrane covering the flexible wire means, whereby flexing of the flexible wire means results in lead expansion and positioning of at least one of the therapy delivery elements closer to or further from the targeted tissue.
 51. An implantable paddle-like lead for providing treatment therapy to targeted tissue of a body comprising: (a) a ventral side having at least one therapy delivery elements; (b) at least one gear mechanism attached to the lead capable of rotating; and (e) at least one arm coupled to the gear; whereby rotation of at least one arm results in lead expansion and positioning of at least one of the therapy delivery elements closer to or further from the targeted tissue.
 52. A method for providing treatment therapy to a targeted neural tissue by means of a therapy delivery device and at least one therapy delivery element coupled to the therapy delivery device, the method comprising the steps of: (a) implanting at least one lead having at least one therapy delivery element within a bone so that the therapy delivery element lies within the bone and in communication near a the targeted tissue; (b) coupling a proximal end of the lead to the therapy delivery device; and (c) operating the therapy delivery device to provide treatment therapy to the targeted tissue via the implanted therapy delivery element.
 53. A method of claim 52 , the bone is a vertebral bone. 